The present invention relates to supplying radio frequency (RF) signals of medium or high power, at different frequencies, particularly in the field of scientific instrumentation using nuclear magnetic resonance (NMR), and has for its object a device for generating RF signals at multiple frequencies.
At present, in most cases of supplying RF signals at different frequencies and with a certain power level, as many couples (source/amplifier) are used as there are signals of different frequencies to be delivered, the source and the amplifier of each couple being designed and adapted to the corresponding frequency band.
This results in a complex structure, each amplifier requiring a particular supply, and very rigid in terms of characteristics and parameters.
Different solutions have been proposed to seek to overcome these drawbacks, by reducing the number of amplifiers.
However, these solutions do not give satisfaction, either because the signals produced do not have the power, or the qualities and/or the desired purity of frequency, or because the construction of the obtained embodiment was even more complex or at least as complex, particularly as to supply, as the conventional solution because of the use of an equivalent number of components or of active circuits.
The problem faced by the present invention consists accordingly in providing a structure of a generator device of the mentioned type, delivering signals with characteristics equivalent to those of the conventional solution described above, and comprising only one wideband amplifier circuit and without another additional active circuit except modulated signal sources.
To this end, the present invention has for its object a device for generating radio frequency electric signals, delivering at least two separate signals having different frequencies, in the form of signals delivered by different primary sources and amplified for the predetermined gain, characterized in that it comprises, in addition to said primary sources, on the one hand, a combining circuit, combining together, without intermodulation, the signals delivered by the primary sources, on the other hand, a signal channel wideband power amplifier having the baseband adapted to the different frequencies of the signals present in the combined signal from the combining circuit, and, finally, by a multi-channel selection and routing unit with a parallel structure, of which each channel delivers at the output an amplified signal at a frequency characteristic of one of the primary sources and comprises a filter circuit adjusted to be passing for one of the different frequencies characteristic of the different primary sources, and piece adaptation circuit and a rejection circuit for other frequencies than the passing frequency of the filter circuit of the channel in question.
A basic principle of the invention accordingly consists in combining, without mixing them, the elementary signals from different sources, passing them along a single channel toward a single amplification circuit, then selectively extracting from the amplified combined signal the different elemental signals and delivering, at the level of separate outlets, amplified elementary signals.
The invention also relates to a device for analyzing with nuclear magnetic resonance with several probes or measuring heads, particularly a spectrometer, characterized in that the measuring heads or probes are supplied by a generating device as mentioned above.